Method for treating chronic wounds with an extracellular polymeric substance solvating system

ABSTRACT

Chronic wounds may be treated by debriding necrotic and other devitalized tissue from the wound, and applying to the wound an extracellular polymeric substance solvating system comprising a metal ion sequestering agent, surfactant and buffering agent. The solvating system disrupts biofilms which may be present in the wound and aids or enables the resumption of normal healing.

FIELD OF THE INVENTION

This invention relates to chronic wound treatment.

BACKGROUND

Chronic wounds affect millions of people, and are responsible forsignificant hospitalization costs and other expenses and inconvenience.Diabetics and people with other circulation impairments are susceptibleto diabetic ulcers and venous stasis ulcers. Paralyzed, unconscious orseverely debilitated patients are susceptible to decubitus ulcers.Although a variety of chronic wound care treatment therapies have beenexplored, many wounds can not be adequately treated. In some casesamputation of an affected limb may be the only available remedy.

SUMMARY OF THE INVENTION

We have found that chronic wounds may be treated by debriding at leastsome necrotic or other devitalized tissue from the wound, and applyingto healthy or healable tissue in the wound an extracellular polymericsubstance (EPS) solvating system comprising a metal ion sequesteringagent, surfactant and buffering agent. The debriding and applicationsteps desirably are combined by applying the solvating system using asufficient flow rate or sufficient pressure to debride at least somedevitalized tissue from the wound.

The invention provides in another aspect a method for treating a chronicwound, which method comprises applying to healthy or healable tissue inthe wound an EPS solvating system comprising a metal ion sequesteringagent, surfactant and buffering agent and having a an osmolarity ofabout 1,000 to about 4,000 milliosmoles (mOsm).

The invention provides in another aspect an apparatus for treating achronic wound, comprising a debriding device; a reservoir containing anEPS solvating system comprising a metal ion sequestering agent,surfactant and buffering agent, in fluid communication with anapplicator for applying the solvating system to a wound; and anaspirating device which removes at least some debrided necrotic or otherdevitalized tissue and excess solvating system from the wound. Thesolvating system applicator desirably also serves as the debridingdevice by applying the solvating system at a sufficient flow rate orunder sufficient pressure to debride at least some devitalized tissuefrom the wound.

The invention provides in another aspect a patient care kit for treatinga chronic wound, the kit comprising a tray; syringe; vessel containingan EPS solvating system comprising a metal ion sequestering agent,surfactant and buffering agent; and printed instructions describing theproper use of the kit for treating chronic wounds.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view of a chronic leg wound being treated withthe disclosed solvating system;

FIG. 2 is a perspective view of an apparatus for treating chronicwounds; and

FIG. 3 is a perspective view of a home care kit for treating chronicwounds.

Like reference symbols in the various figures of the drawing indicatelike elements. The elements in the drawing are not to scale.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following detailed description describes certain embodiments and isnot to be taken in a limiting sense. All weights, amounts and ratiosherein are by weight, unless otherwise specifically noted. The termsshown below have the following meanings:

The phrase “antimicrobial agent” refers to a substance having theability to cause greater than a 90% numeric reduction (viz., at least a1-log order reduction) in a population of one or more aerobic oranaerobic bacteria present in chronic wounds.

The terms “attached” and “adhered” when used in reference to a bacterialbiofilm and a surface mean that the biofilm is established on and atleast partially coats or covers the surface, and has some resistance toremoval from the surface. As the nature of this relationship is complexand poorly understood, no particular mechanism of attachment oradherence is intended by such usage.

The phrase “bacterial biofilm” means a community of bacteria attached toa surface, with the organisms in the community being contained within anEPS matrix produced by the bacteria.

The term “biocompatible” when used in reference to a substance meansthat the substance presents no significant deleterious or untowardeffects upon the body.

The phrase “chronic wound” means a wound containing exposed devitalizedor otherwise compromised tissue which will not heal in a medicallyacceptable time frame (e.g., within one or two months) through normalhealing processes.

The term “debride” when used in reference to devitalized tissue attachedwithin a chronic wound means to cut away or otherwise excise the tissueso that it is no longer attached. No particular mechanism of debridementis intended by such usage.

The terms “detaching”, “removing” and “disrupting” when used inreference to a bacterial biofilm attached or adhered to a surface meanthat at least a significant amount of the biofilm initially present onthe surface no longer is attached or adhered to the surface. Noparticular mechanism of detachment, removal or disruption is intended bysuch usage.

The term “devitalized” when used in reference to wound tissue meanstissue that is sufficiently devoid of life so that it will not heal ifleft untreated.

The term “osmolality” means the number of osmoles of solute per kilogramof solvent, as measured using a Model 5002 Osmette A™ freezing pointdepression osmometer (Precision Systems, Inc.).

The term “osmolarity” means the number of osmoles of solute per liter ofsolution. Osmolarity may conveniently be calculated from an osmolalitymeasurement.

The phrase “sequestering agent” means a chemical that will combine withanother material, especially a metal ion, to discourage or prevent thematerial from coming out of solution. The phrase “metal ion sequesteringagent” means a sequestering agent that will combine with one or moremetal ions such as alkali metals (viz., lithium, sodium, potassium,rubidium, cesium or francium), alkaline earth metals (viz., beryllium,magnesium, calcium, strontium, barium or radium), iron and the like todiscourage or prevent the metal ion from coming out of solution.

The term “solvating” means to form a solution or dispersion containing asolvent or other carrier within which a solute is dissolved orsuspended.

The term “wound” means an opening in the skin through which subdermal ordeeper tissue (e.g., subcutaneous fat, muscle or other tissue) isexposed.

Referring to FIG. 1, a leg 10 with chronic wound 12 (in this instance, avenous stasis ulcer) may be treated using a hydrodebriding device 14which applies the disclosed EPS solvating system to wound 12 at asufficient flow rate or under sufficient pressure to debride devitalizedtissue. A variety of devices may be used or adapted as need be toprovide device 14, including the Pulsavac™ and Pulsavac Plus™ wounddebridement systems (Zimmer, Inc.), the SonicOne™ ultrasonic wounddebridement system (Misonix, Inc.), the Versajet™ hydrosurgery system(Smith & Nephew, Inc.), the SpineJet™ hydrosurgery system (HydroCision,Inc.) and the MHS™ hydrodebriding system (Medtronic Xomed, Inc.). Device14 may include or be connected to a suitable power source (e.g., arechargeable battery or low voltage transformer) to operate a pump (notshown in FIG. 1) within device 14. The solvating system may be appliedfrom a reservoir such as bag 16 in fluid communication via conduit 18and valve 20 with device 14. Sterile saline or other suitable rinsingsolution may if desired be supplied from a reservoir such as bag 22 influid communication via conduit 24 and valve 26 with device 14. Ifdesired, other debridement techniques may be employed together withdevice 14, including cutting or scraping away devitalized tissue using ascalpel, scissors, swab, plastic stick, tongue depressor or othersuitable tool such as the Straightshot™ M4 microdebrider (MedtronicXomed, Inc.). The debrided devitalized tissue, wound exudates, excesssolvating system solution, excess saline or other rinsing solution (ifused) and other solid or fluid residues may be collected in pan 24.Absorbent pad 26 made from a nonwoven or other suitable material mayhelp retain at least the fluid residues in pan 24. At the conclusion oftreatment, a wound dressing (not shown in FIG. 1) may if desired beapplied to wound 12 to discourage further infection.

FIG. 2 shows a perspective view of another apparatus 200 for use in thedisclosed method. A variety of devices may be used or adapted as need beto provide apparatus 200, including the V.A.C. Instill™ wound healingsystem from KCl Licensing (San Antonio, Tex.), and the Invia™ healingsystem or the Dominant™ 35c/I suction system (both from MedelaHealthcare U.S.). Apparatus 200 includes a housing 202 with handle 204.Touch screen display 206 may be used to control the operation ofapparatus 200. The disclosed solvating system may be supplied from a bagor other suitable reservoir (for example, a bag like bag 16 in FIG. 1)to a chronic wound via tubing 208. The coiled end of tubing 208 may beconnected to a suitable dispensing tip (not shown in FIG. 2) throughwhich the disclosed solvating system may be delivered into a wound.Shoulder clamp 210 may be used to hold tubing 208 on apparatus 200.Debrided devitalized tissue, wound exudates, excess solvating systemsolution, excess saline or other rinsing solution (if used) and othersolid or fluid residues may be collected from the wound using a suitableaspirating tip (not shown in FIG. 2) connected to the coiled end oftubing 212. The other end of tubing 212 is attached to a fitting 215 onhousing 202 through which the collected solid or fluid residues passinto a pump (not shown in FIG. 2) inside housing 202. Shoulder clamp 214may be used to hold tubing 212 on apparatus 200. A removable canister216 may be used to collect and later dispose of solid and fluid residuespassing through the pump. Release button 218 and an associated clamp orother retaining mechanism (not shown in FIG. 2) may be used to lockcanister 216 in apparatus 200 until such time as removal of canister 216is desired.

The apparatus shown in FIG. 2 does not itself deliver the disclosedsolvating system to the wound. Debridement of devitalized tissue couldbe carried out using any convenient debridement technique including thecutting or scraping techniques mentioned above, or by excising thedevitalized tissue using a separately-supplied directed fluid streamsuch as a pressurized sterile saline stream. The FIG. 2 apparatus may ifdesired be altered to permit pressurized delivery of solvating systemsolution, for example by adding a suitable separate pump, or bymodifying the existing pump or associated tubing in apparatus 200 sothat sufficient flow rate or sufficient pressure for hydrodebriding andsufficient suction for removal of solid and fluid residues from woundsare available in apparatus 200. The FIG. 2 apparatus may also bemodified to provide additional measures for discouraging bacterialsurvival, regrowth or recolonization in the wound, including exposure ofthe wound to light (e.g., ultraviolet and other wavelengths of light,delivered as non-coherent or as laser radiation), sonication (e.g.,ultrasound), gases (e.g., nitrogen or oxygen), heating, cooling, oragents which consume, complex, bind to or replace bacteria or bacterialnutrients such as iron or sugars.

FIG. 3 shows a perspective view of a patient care kit 300 (e.g., a homecare kit or travel kit) which may be employed in the disclosed method.Kit 300 includes tray 302 which may be lined with absorbent pad 304.Tray 302 may also contain or otherwise be packaged with syringe 306,printed instructions 308 describing the proper use of kit 300 in thehome treatment of chronic wounds, and bottle 310 or other suitablevessel containing the disclosed solvating system. Kit 300 may alsoinclude one or more manual debriding tools (not shown in FIG. 3) such asa scissors, knife or swab and one or more wound dressings (also notshown in FIG. 3) for application to the wound following treatment.Syringe 306 may for example have a capacity of about 50 to about 75 cc(e.g., about 60 cc), and bottle 310 may for example have a capacity ofabout 2 to 5 times the capacity of syringe 306. Kit 300 may be soldover-the-counter or by prescription, with prescription sale beingpreferred in cases where further wound monitoring by a health careprofessional may be needed once kit 300 and any permitted solvatingsystem refills have been consumed.

Chronic wounds treatable using the disclosed method wound typically willcontain large colonies of one or more aerobic or anaerobic organismsoccupying one or more biofilms. For long-term chronic wounds, moreanaerobes than aerobes may be present. Representative organisms whichmay be present in chronic wound biofilms include Staphylococcus species(e.g., normal skin flora including S. epidermidis, S. Corynebacteriumand S. Brevibacterium, and typical pathogens including S. aureus), othernormal skin flora including Proprionibacterium acnes, and otherpathogens, for example Acinetobacter species including A. baumannii,Bacillus species including B. anthracis, Brucella species including B.melitensis, Clostridium species including C. tetani, Corynebacteriumspecies including C. diphtheriae, Erysipelothrix species including E.rhusiopathiae, Escherichia species including E. coli, Klebsiella speciesincluding K. pneumoniae or K. oxytoca, Leptospira species including L.interrogans, Mycobacteria species including M. marinum or M. ulcerans,Proteus species including P. mirabilis, P. vulgaris or P. penneri,Pseudomonas species including P. aeruginosa or P. maltophilia,Stenotrophomonas species including S. maltophilila, Beta-hemolyticStreptococcus species including S. pyogenes or S. agalactiae, Treponemaspecies including T. pallidum, and Yersinia species including Y. pestis.

The wound may exhibit festering or other exudate production, swelling,erythema, pain, localized increased temperature, periwound cellulitis,ascending infection or a change in the appearance of granulation tissue(for example, discoloration, bleeding or friability). The wound may havebeen caused or aggravated due to a variety of external factors includingabrasion, burns, compression, immersion, surgery or trauma. Frequentlyhowever the wound may be caused or aggravated and may remain chronic dueto a variety of internal factors including a compromised circulatorysystem (e.g., as in many diabetic patients), a compromised immune systemor diseases including impetigo, folliculitis, erysipelas, cellulitis ornecrotizing fasciitis. Chronic foot or leg wounds in diabetic patientsfrequently involve colonies of S. aureus and Beta-hemolyticStreptococcus, are especially difficult to heal, and are of particularinterest for treatment using the disclosed method since doing so mayavoid amputation. The wound may be present in other body parts or inother extremities, and may be present not only in humans (includingadults, children and the elderly) but also in animals (includinglivestock, pets, show animals and wild animals).

The disclosed solvating system may be used to break down bacterialbiofilms in chronic wounds and consequently aid in biofilm detachment,removal or disruption. The solvating system preferably is biocompatiblewith healthy and healable wound tissues, and desirably does not containingredients which might potentially harm such tissues or undulycompromise wound healing. The solvating system desirably has asufficiently low viscosity to enable easy delivery to the wound usingfor example power spray or other spray application, lavage, misting,mopping, wicking or dripping. The solvating system desirably also may beeasily removed from the treatment site by subsequent aspiration,flushing, rinsing, draining or absorption (e.g., using an absorbent pador other suitable material). While not wishing to be bound by theory,the metal ion sequestering agent may complex, bind or otherwise tie upmetal ions which may crosslink, bridge or otherwise assist in bindingtogether the polymer chains in an EPS matrix. The solvating agent maythen surround the unbound polymer chains or fragments, breaking down thematrix, solvating the unbound polymer chains or fragments, and bringingthem into solution or suspension where they can be easily flushed orotherwise removed from the wound site using for example additionalamounts of the solvating system or a separate rinsing agent.

Solvating systems for use in certain tissue treatments are described inU.S. Patent Application Publication No. US 2007/0264296 A1 and PCTPublished Application No. WO 2007/134055 A1. The solvating systemsdescribed in these publications have particular utility in ear, nose andthroat applications such as the treatment of otitis media, cholesteatomaand rhinosinusitis. In general, these solvating systems haveinsufficient osmolarity for the efficacious treatment of chronic wounds,but they may be adapted for use in treating chronic wounds. Ciliatedtissue such as that found in the ear, nose and throat is somewhatfragile, and to avoid damaging the cilia it is desirable to usesolvating systems with low osmolarity, e.g., osmolarity of about 300 toabout 900 mOsm. When treating chronic wounds, it is preferable to use asubstantially higher osmolarity EPS solvating system, for example onewhose osmolarity is about 1,000 to about 4,000 mOsm, more preferablyabout 1,500 to about 2,600 mOsm. Doing so may facilitate wound treatmentor wound healing.

The metal ion sequestering agent desirably is a mild acid whose acidityis sufficient to sequester one or more metal ions in the EPS matrix, butwhich is not so acidic so as to harm healthy or healable wound tissue.Metal ions of particular interest (due to their likely involvement inthe targeted bacterial biofilms) include sodium, calcium and iron. Themetal ion sequestering agent desirably is water-soluble and not undulytoxic. Representative acids include but are not limited to carboxylicacids, diacids, or triacids such as formic acid, acetic acid,chloroacetic acid, dichloroacetic acid, oxalic acid, oxamic acid,glycolic acid, lactic acid, pyruvic acid, aspartic acid, fumaric acid,maleic acid, succinic acid, iminodiacetic acid, glutaric acid,2-ketoglutaric acid, glutamic acid, adipic acid, citric acid, glucuronicacid, mucic acid, nitrilotriacetic acid, salicylic acid, ketopimelicacid, benzoic acid, mandelic acid, chloromandelic acid, phenylaceticacid, phthalic acid and boric acid; mineral acids such as hydrochloricacid, orthophosphoric acid and phosphonic acid; and mixtures thereof.Citric acid is a preferred acid. The metal ion sequestering agent mayfor example be present at a concentration of at least about 0.01 M, atleast about 0.05 M or at least about 0.1 M, e.g., about 0.01 to about1.5 M. Increased metal ion sequestering agent amounts may promote fasterbiofilm breakup.

The solvating system also includes a surfactant. The surfactantdesirably is water-soluble and nontoxic. Exemplary surfactants includeanionic surfactants, nonionic surfactants, cationic surfactants andzwitterionic surfactants. Exemplary anionic surfactants include but arenot limited to C₆-C₂₄ alkylbenzene sulfonates; C₆-C₂₄ olefin sulfonates;C₆-C₂₄ paraffin sulfonates; cumene sulfonate; xylene sulfonate; C₆-C₂₄alkyl naphthalene sulfonates; C₆-C₂₄ alkyl or dialkyl diphenyl ethersulfonates or disulfonates, C₄-C₂₄ mono or dialkyl sulfosuccinates;sulfonated or sulfated fatty acids; C₆-C₂₄ alcohol sulfates (for exampleC₆-C₁₂ alcohol sulfates); C₆-C₂₄ alcohol ether sulfates having 1 toabout 20 ethylene oxide groups; C₄-C₂₄ alkyl, aryl or alkaryl phosphateesters or their alkoxylated analogues having 1 to about 40 ethylene,propylene or butylene oxide units; and mixtures thereof. For example,the anionic surfactant may be sodium chenodeoxycholate,N-lauroylsarcosine sodium salt, lithium dodecyl sulfate,1-octanesulfonic acid sodium salt, sodium cholate hydrate, sodiumdeoxycholate, sodium dodecyl sulfate (also known as sodium laurylsulfate) or sodium glycodeoxycholate.

Exemplary cationic surfactants include but are not limited to quaternaryamine compounds having the formula:

where R, R′, R″ and R′″ are each a C₁-C₂₄ alkyl, aryl or aralkyl groupthat can optionally contain one or more P, O, S or N heteroatoms, and Xis F, Cl, Br, I or an alkyl sulfate. For example, the cationicsurfactant may be hexadecylpyridinium chloride monohydrate orhexadecyltrimethylammonium bromide.

Exemplary nonionic surfactants include but are not limited to C₆-C₂₄alcohol ethoxylates (for example C₆-C₁₄ alcohol ethoxylates) having 1 toabout 20 ethylene oxide groups (for example about 9 to about 20 ethyleneoxide groups); C₆-C₂₄ alkylphenol ethoxylates (for example C₈-C₁₀alkylphenol ethoxylates) having 1 to about 100 ethylene oxide groups(for example about 12 to about 20 ethylene oxide groups); C₆-C₂₄alkylpolyglycosides (for example C₆-C₂₀ alkylpolyglycosides) having 1 toabout 20 glycoside groups (for example about 9 to about 20 glycosidegroups); C₆-C₂₄ fatty acid ester ethoxylates, propoxylates orglycerides; C₄-C₂₄ mono or di alkanolamides; and mixtures thereof. Forexample, the nonionic surfactant may be polyoxyethyleneglycol dodecylether, N-decanoyl-N-methylglucamine, digitonin, n-dodecyl B-D-maltoside,octyl B-D-glucopyranoside, octylphenol ethoxylate, polyoxyethylene (8)isooctyl phenyl ether, polyoxyethylene sorbitan monolaurate orpolyoxyethylene (20) sorbitan monooleate.

Exemplary zwitterionic surfactants include but are not limited toaminoalkylsulfonate compounds having the formula:

where R, R′, R″ and R′″ are each a C₁-C₂₄ alkyl, aryl or aralkyl groupthat can optionally contain one or more P, O, S or N heteroatoms; amineoxide compounds having the formula:

where R, R′ and R″ are each a C₁-C₂₄ alkyl, aryl or aralkyl group thatcan optionally contain one or more P, O, S or N heteroatoms; and betainecompounds having the formula:

where R, R′ and R″ are each a C₁-C₂₄ alkyl, aryl or aralkyl group thatcan optionally contain one or more P, O, S or N heteroatoms, and n isabout 1 to about 10. For example, the zwitterionic surfactant may be3-[(3-cholamidopropyl) dimethylammonio]-2-hydroxy-1-propane sulfonate,3-[(3-cholamidopropyl) dimethylammonio]-1-propane sulfonate (sometimesreferred to as CHAPS),3-(decyldimethylammonio) propanesulfonate innersalt (sometimes referred to as caprylyl sulfobetaine), orN-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate.

Preferred surfactants include alkyl sulfates, alkyl sulfonates, arylsulfonates and zwitterionic surfactants. The desired surfactants may beobtained as pure compounds or in some instances may be obtained by usingproducts such as liquid Castile soap. The surfactant may for example bepresent at a concentration of at least about 0.002 M, at least about0.005 M or at least about 0.01 M, e.g., about 0.002 to about 1 M, about0.005 to about 0.7 M or about 0.01 to about 0.5 M. Expressed on a weightbasis, the surfactant preferably is greater than 0.2 wt. % of thesolvating system and may for example be about 0.3% to about 30%, about0.5% to about 25% or about 1% to about 20% of the solvating system.Increased surfactant amounts may promote faster biofilm breakup.

The solvating system also includes a buffering agent. The bufferingagent preferably maintains the solvating system at an appropriate pH forcontacting the wound, e.g., at a pH greater than about 4 or greater thanabout 5. For example, the solvating system may be buffered to have anear-neutral pH, e.g., a pH greater than about 5 and less than about8.5. Buffering agents may for example be up to about 50% of thesolvating system. Exemplary buffering agents include but are not limitedto potassium chloride, glycine, potassium hydrogen phthalate, sodiumacetate, potassium hydrogen phthalate, barbitone sodium and sodiumcitrate. When the metal ion sequestering agent is a mild acid, thebuffering agent desirably is a salt of that acid.

The solvating system also includes water. The water may be distilled,deionized or sterile water. Water may for example be at least 50%, atleast 60% or at least 75% of the solvating system.

The solvating system may optionally include various other ingredients,including nonaqueous solvents (e.g., alcohols), antimicrobial agents,therapeutic agents and a variety of adjuvants. Solvating systems whichdo not contain antimicrobial agents may be preferred for someapplications, for example where there may be a risk that anantimicrobial agent might promote the evolution of more resistantbacteria. Solvating systems containing one or more antimicrobial agents,and especially one or more topical antibiotic agents (viz., antibioticswhich may be applied to the skin and which in connection with thedisclosed method are applied in a chronic wound), may be preferred forother applications. The EPS matrix may allow a biofilm to stick to anunderlying tissue surface while protecting the embedded organisms. Thebacteria in such a biofilm may be approximately 100 to 1000 times moreresistant to the effects of antibiotics than planktonic bacteria. Afterthe biofilm has been broken down into unbound polymers or fragments andsolvated or otherwise disrupted by the solvating system, anantimicrobial agent can much more effectively attack the remainingbacteria. Exemplary antimicrobial agents include active oxygen compoundssuch as hydrogen peroxide, isolated or equilibrium derived or isolatedperacids such as chloroperbenzoic acids, peracetic acid, perheptanoicacid, peroctanoic acid, perdecanoic acid, performic acid, percitricacid, perglycolic acid, perlactic acid, perbenzoic acid, and monoesterperacids derived from diacids or diesters such as adipic, succinic,glutaric, or malonic acid; amphenicols; ampicillins; ansamycins;beta-lactams such as carbacephems, carbapenems, cephalosporins,cephamycins, monobactams, oxacephems, penicillins and any of theirderivatives; carboxylic esters such as p-hydroxy alkyl benzoates andalkyl cinnamates; chitosan salts; cubic-phase lipids; gallium-containingantimicrobial agents such as gallium acetylacetonate, gallium bromide,gallium chloride, gallium fluoride, gallium iodide, gallium maltolate,gallium nitrate, gallium nitride, gallium percolate, gallium phosphideand gallium sulfate; iodo-compounds and other active halogen compoundssuch as iodine, interhalides, polyhalides, metal hypochlorites,hypochlorous acid, metal hypobromites, hypobromous acid, chloro- andbromo-hydantoins, chlorine dioxide and sodium chlorite; lincosamides;macrolides; nitrofurans; organic peroxides including benzoyl peroxideand alkyl benzoyl peroxides; ozone; phenolic derivatives includingo-phenyl phenol, o-benzyl-p-chlorophenol, tert-amyl phenol and C₁-C₆alkyl hydroxy benzoates; quaternary ammonium compounds such asalkyldimethylbenzyl ammonium chloride and dialkyldimethyl ammoniumchloride; quinolines; singlet oxygen generators; sulfonamides; sulfones;sulfonic acids such as dodecylbenzene sulfonic acid; tetracyclines;vancomycin; derivatives thereof and mixtures thereof. Many of theserecited agents represent classes containing useful specific materialswhose individual utility will be recognized by persons having ordinaryskill in the art. For example, exemplary penicillins include but are notlimited to amdinocillin, amdinocillin pivoxil, amoxicillin ampicillin,apalcillin, amoxicillin, axidocillin, azlocillin, acampicillin,bacampicillin, benzylpenicillinic acid, benzylpenicillin sodium,carbenicillin, carindacillin, clometocillin, cloxacillin, cyclacillin,dicloxacillin, epicillin, fenbenicillin, floxacillin, hetacillin,lenampicillin, metampicillin, methicillin sodium, mezlocillin, nafcillinsodium, oxacillin, penamecillin, penethamate hydriodide, penicillin Gbenethamine, penicillin G benzathine, penicillin G benzhydrylamine,penicillin G calcium, penicillin G hydrabamine, penicillin G potassium,penicillin G. procaine, penicillin N, penicillin O, penicillin V,penicillin V banzathine, penicillin V hydrabamine, penimepicycline,phenethicillin potassium, piperacillin, pivampicillin propicillin,quinacillin, sulbenicillin, sultamicillin, talampicillin, temocillin,ticarcillin and mixtures thereof or with other materials (e.g.,penicillins combined with clavulanic aid such as the combination ofamoxicillin and clavulanic acid available as Augmentin™ fromGlaxoSmithKline).

Preferably the antimicrobial agent provides greater than a 99% numericreduction (viz., at least a 2-log order reduction), greater than a 99.9%numeric reduction (viz., at least a 3-log order reduction), greater thana 99.99% numeric reduction (viz., at least a 4-log order reduction) orgreater than a 99.999% numeric reduction (viz., at least a 5-log orderreduction) in a population of one or more aerobic or anaerobic bacteriapresent in chronic wounds.

Exemplary therapeutic agents include any material suitable for use inwound treatment including analgesics, anti-cholinergics, anti-fungalagents, steroidal or non-steroidal anti-inflammatory agents,anti-parasitic agents, antiviral agents, biostatic compositions,chemotherapeutic/antineoplastic agents, cytokines, immunosuppressors,nucleic acids, peptides, proteins, steroids, vasoconstrictors, vitamins,mixtures thereof, and other therapeutic materials. Bacterially selectivepeptides may, for example, provide a more useful or safer therapeuticeffect against some pathogens than that provided by broad spectrumantibiotics.

Adjuvants which may be included in the solvating system include dyes,pigments or other colorants (e.g., FD & C Red No. 3, FD & C Red No. 20,FD & C Yellow No. 6, FD & C Blue No. 2, D & C Green No. 5, D & C OrangeNo. 4, D & C Red No. 8, caramel, titanium dioxide, fruit or vegetablecolorants such as beet powder or beta-carotene, turmeric, paprika andother materials that will be familiar to those skilled in the art);indicators; antioxidants; antifoam agents; and rheology modifiersincluding thickeners and thixotropes.

The wound may be debrided to detach devitalized tissue using manualdebriding tools such as those described above. Preferably the wound isdebrided using a directed stream of the disclosed solvating system orother suitable fluid. The flow rate or pressure desirably are highenough to promote rapid and sufficiently complete debriding, and lowenough to avoid undue pain or injury to healthy or healable woundtissue. At least part and preferably all of the devitalized wound tissueis debrided.

The solvating system desirably is applied to at least an extentsufficient to cover healthy or healable tissue in the wound. In someinstances it will be desirable to apply the solvating system within andnot merely atop exposed tissue within the wound. Sufficient solvatingsystem should be applied to the wound and to a targeted biofilmcontained therein so that the biofilm and its organisms are wholly orpartially disrupted, solvated or removed, either during treatment or atsome subsequent time. Doing so may involve chemical dilution ormechanical disruption, and may be accompanied by breakdown of thebiofilm EPS matrix through calcium ion sequestering by the metal ionsequestering agent, and by solvation of the resulting breakdownfragments (e.g., mannuronic and guluronic acids) into aqueous solutionso as to facilitate their removal using aspiration, lavage or otherremoval techniques. High flow rates (for example, more than 7 and lessthan 20 cm³/sec) or high delivery pressures (for example, about 30 toabout 500 KPa or about 60 to about 350 KPa, as measured at the pumpoutlet when the desired application tip is attached) may assist in wounddebridement and biofilm disruption. It may be desirable to applysufficient solvating system into the wound to displace any pus or otherwound exudates which may be present, allowing excess solvating system tooverflow from the wound until the color of the excess solvating systemno longer changes. The solvating system may be left in place until itcan drain away or is otherwise eliminated or resorbed, or the solvatingsystem may be allowed to stand for a suitable time (e.g., a few minutes,a few hours or longer) and then may be rinsed away using sterile salineor another suitable liquid. Application of the solvating system andremoval of dislodged or disrupted biofilm and bacteria may also berepeated as desired for more thorough removal of the offendingorganisms.

The solvating system may desirably be used as a part of a multi-steptreatment regimen which disrupts the bacterial biofilm and discouragesits return. For example, a series of steps that may be broadlyclassified as Cleansing/Disrupting, Killing, Protecting/Coating,Aerating, and Healing may be carried out. The Cleansing/Disrupting stepmay be carried out by applying the solvating system to a chronic woundas described above. The Killing step may be carried out by applying asuitable antimicrobial agent to the wound site. This may for example beaccomplished by including an antimicrobial agent in the solvating systemor by separately applying such an agent intra operatively or postoperatively (e.g., topically, orally or systemically). The Killing stepmay employ additional measures to discourage bacterial survival,regrowth or recolonization in the wound, e.g., as discussed above inconnection with the FIG. 2 apparatus. The Protecting/Coating step may becarried out by coating at least part of the treated wound with aprotective sealant layer. The sealant may provide a variety of benefitssuch as discouraging or preventing recolonization of the wound withbacteria and new biofilm-forming colonies; reducing inflammation;improving wound healing or allowing for the recovery of the body'snatural innate immune response. The sealant may include one or moreantimicrobial agents to further attack any bacterial biofilm, biofilmfragments or bacteria remaining following the Cleansing/Disrupting stepdescribed above, and to discourage its or their return. A preferredsealant may be based on the sealant disclosed in U.S. Patent PublicationNo. US 2007/0264310 A1, filed Apr. 24, 2007. The Aerating step may becarried out by applying a wound dressing with a suitable opening oropenings (e.g., slits or pores) and leaving it or them open for a periodof time sufficient to allow aeration of the treated wound. The Healingstep may be carried out by allowing the cleansed, protected andoptionally sealed wound to undergo a return to a normal state, e.g.,through one or more normal healing mechanisms such as an inflammatoryresponse, fibroblast proliferation and wound remodeling.

The invention is further described in the following Example, in whichall parts and percentages are by weight unless otherwise indicated.

Example

Biofilm formation. Pseudomonas aeruginosa PAO1 (ATCC number: BAA-47),Enterococcus faecalis V583 (ATCC number: 700802), and Staphylococcusaureus Mu50 (ATCC number: 700699) grown on agar plates made from trypticsoy broth (TSB, Sigma Chemical Co., St. Louis, Mo., USA) were inoculatedinto TSB broth and grown at 37° C. in a shaker for 16 hr. An aliquot wasdiluted in TSB broth to a series of dilutions for each individualbacteria type. The diluted bacteria were plated out to count colonyforming units (CFU). They were further diluted to 1×10⁶ cfu ml⁻¹ andmixed equally as inoculums. Bolton broth (Oxoid Ltd, Basingstock,Hampshire, England) with 50% Bovine plasma (Biomeda, Foster City,Calif., USA) was used for biofilm formation media. Glass 16×150 mm testtubes with caps were autoclaved, and 7 ml biofilm formation mediaaseptically dispensed in each tube. The normalized cultures of the threebacteria were mixed and 10 μl portions of the combined and normalized1×10⁶ CFU ml⁻¹ culture were inoculated into glass tubes by ejecting thepipette tips into the tubes. The pipette tip acts as a surface forbiofilm formation. The tubes were then grown at 37° C. in a shaker for24 hours at 140 rpm.

Solvating system preparation. A solvating system (referred to below as“CAZS”) was prepared at four osmolarity levels by combining deionizedwater, caprylyl sulfobetaine zwitterionic surfactant(CH₃(CH₂)₉N⁺(CH₃)₂CH₂CH₂CH₂SO₃ ⁻, CAS15163-36-7), citric acid (CAS77-92-9) and sufficient sodium citrate (CAS 6132-04-3) to buffer thesystem to pH 5.5, using the amounts shown below in Table 1:

TABLE 1 Osmolarity, mOsm Ingredient 830 1,586 3,628 CaprylylSulfobetaine (g/L) 5.08 5.15 5.35 Citric Acid (g/L) 5.78 12.5 25 SodiumCitrate (g/L) 55.13 120.5 240.5 pH 5.5 5.5 5.5

Incubation with formed biofilms. In a series of runs the formed biofilmswere washed and then incubated with the three CAZS solutions, thenassociated with a 30 μg/ml solution of Gentamicin sulfate (MPBiomedicals, Illkirch, France) in distilled water, or with a 20 ppmsolution of 2,4,4′-trichloro-2-hydroxydiphenyl ether (Triclosan, KICChemicals, New Paltz, N.Y., USA) dissolved in propylene glycol(ScienceLab, Houston, Tex., USA). The resulting mixtures were stirred at37° C. and 140 rpm for 1, 2, 3 and 4 hours. Biofilm formation wassubjectively observed and the biofilms were collected. A set of tubeswith biofilms were placed in an oven at 80° C. for 48 hours to obtain adry weight. The biomass dry weight was measured as the total weightminus the empty tube weight measured before use. Tests were performed intriplicate for each treatment group. A separate set of tubes intriplicate was used for DNA extraction and quantitative PCR analysis todetermine relative bacterial levels in the treated biofilms. The resultsfor the 830 and 1,586 mOsm CAZS solutions are shown below in Table 2:

TABLE 2 Dry Relative Bacterial Levels Weight, P. Sample mg aeruginosa E.faecalis S. aureus Control 126 46.8 29.7 23.5 20 mg/ml Gentamicin 78 0.250.3 49.6 20 mg/ml Gentamicin + 68.5 0.2 49.7 50.1 200 μl 830 mOsm CAZS20 mg/ml Gentamicin + 68 0.1 62.2 37.8 200 μl 1,586 mOsm CAZS 20 ppmTriclosan 88 60.0 39.9 0.13 20 ppm Triclosan + 200 28.5 53.0 47.0 0.1 μl830 mOsm CAZS 20 ppm Triclosan + 200 15 69.1 30.9 0.1 μl 1,586 mOsm CAZS200 μl 830 mOsm CAZS 115.5 45.0 32.7 22.4 200 μl 1,586 mOsm 87 51.1 35.113.8 CAZS

The results in Table 2 show that the biofilm dry weight was reducedusing all treatments. Biofilm dry weight was also reduced using the CAZSsolution alone, and further reduced when used in combination withTriclosan. CAZS solution also appeared to exhibit a selective inhibitoryeffect on S. aureus.

Although specific embodiments have been illustrated and described hereinfor purposes of description of the preferred embodiments, it will beappreciated by those of ordinary skill in the art that a wide variety ofalternate or equivalent implementations calculated to achieve the samepurposes may be substituted for the specific embodiments shown anddescribed without departing from the scope of the present invention.This application is intended to cover any adaptations or variations ofthe preferred embodiments discussed herein. Therefore, it is manifestlyintended that this invention be limited only by the claims and theequivalents thereof.

1. A method for treating chronic wounds, which method comprises: a)debriding at least some necrotic or other devitalized tissue from thewound, and b) applying to healthy or healable tissue in the wound anextracellular polymeric substance solvating system comprising an aqueoussolution of a metal ion sequestering agent, surfactant and bufferingagent.
 2. A method according to claim 1 wherein the debriding andapplying steps are combined by applying the solvating system at asufficient flow rate or using sufficient pressure to debride at leastsome devitalized tissue from the wound.
 3. A method according to claim 1comprising applying the solvating system by spraying, lavage, misting,mopping, wicking or dripping and further comprising removing thesolvating system from the wound by flushing, rinsing, draining orabsorption.
 4. A method according to claim 1 wherein the solvatingsystem has an osmolarity of about 1,000 to about 4,000 milliosmoles ofsolute per liter.
 5. A method according to claim 1 wherein the solvatingsystem has an osmolarity of about 1,500 to about 2,600 milliosmoles ofsolute per liter.
 6. A method according to claim 1 wherein the metal ionsequestering agent comprises a mild acid whose acidity is sufficient tosequester one or more metal ions in a bacterial biofilm but which is notso acidic so as to harm healthy or healable tissue in the wound.
 7. Amethod according to claim 1 wherein the metal ion sequestering agentcomprises a sequestering agent for sodium, calcium or iron.
 8. A methodaccording to claim 1 wherein the metal ion sequestering agent comprisesa carboxylic acid, diacid, triacid or mixture thereof.
 9. A methodaccording to claim 8 wherein the metal ion sequestering agent comprisesformic acid, acetic acid, chloroacetic acid, dichloroacetic acid, oxalicacid, oxamic acid, glycolic acid, lactic acid, pyruvic acid, asparticacid, fumaric acid, maleic acid, succinic acid, iminodiacetic acid,glutaric acid, 2-ketoglutaric acid, glutamic acid, adipic acid,glucuronic acid, mucic acid, nitrilotriacetic acid, salicylic acid,ketopimelic acid, benzoic acid, mandelic acid, chloromandelic acid,phenylacetic acid, phthalic acid, boric acid or mixture thereof.
 10. Amethod according to claim 8 wherein the metal ion sequestering agentcomprises citric acid.
 11. A method according to claim 1 wherein themetal ion sequestering agent is present at a concentration of about 0.01to about 1.5 M.
 12. A method according to claim 1 wherein the surfactantcomprises a zwitterionic surfactant.
 13. A method according to claim 1wherein the surfactant is about 0.3% to about 30% of the solvatingsystem.
 14. A method according to claim 1 wherein the solvating systemcomprises sufficient buffering agent so that the solvating system has apH greater than about
 4. 15. A method according to claim 1 wherein thesolvating system comprises sufficient buffering agent so that thesolvating system has a pH greater than about 5 and less than about 8.5.16. A method according to claim 1 wherein the solvating system furthercomprises an antimicrobial agent.
 17. A method according to claim 16wherein the antimicrobial agent comprises a topical antibiotic.
 18. Amethod according to claim 16 wherein the antimicrobial agent comprises apeptide.
 19. A method according to claim 16 wherein the antimicrobialagent comprises a bacterially selective peptide.
 20. A method accordingto claim 16 wherein the antimicrobial agent comprises galliumacetoacetonate, gallium bromide, gallium chloride, gallium fluoride,gallium iodide, gallium maltolate, gallium nitrate, gallium nitride,gallium percolate, gallium phosphite, gallium sulfate or mixturethereof.
 21. A method according to claim 1 comprising treating a foot orleg wound in a diabetic patient.
 22. A method according to claim 1comprising treating the wound to disrupt a bacterial biofilm anddiscourage its return.
 23. A method for treating a chronic wound, whichmethod comprises applying to healthy or healable tissue in the wound anextracellular polymeric substance solvating system comprising an aqueoussolution of a metal ion sequestering agent, surfactant and bufferingagent and having an osmolarity of about 1,000 to about 4,000milliosmoles of solute per liter. 24-41. (canceled)
 42. An apparatus fortreating a chronic wound, comprising: a) a debriding device; b) areservoir containing an extracellular polymeric substance solvatingsystem comprising an aqueous solution of a metal ion sequestering agent,surfactant and buffering agent, in fluid communication with anapplicator for applying the solvating system to a wound; and c) anaspirating device which removes at least some debrided necrotic or otherdevitalized tissue and excess solvating system from the wound. 43-57.(canceled)
 58. A patient care kit for treating a chronic wound, the kitcomprising a tray; syringe; vessel containing an extracellular polymericsubstance solvating system comprising an aqueous solution of a metal ionsequestering agent, surfactant and buffering agent; and printedinstructions describing the proper use of the kit for treating chronicwounds. 59-67. (canceled)